The use of portable devices to conduct visual acuity functions are known in the art, for example see U.S. Pat. No. 7,771,051, which is incorporated by reference in its entirety.
Additionally, the use of portable devices to conduct metamorphopsia tests using drawn inputs are known in the art, for example see U.S. Pat. No. 8,047,652, which is incorporated by reference in its entirety.
While portable devices exist, the current state of the testing methods used are time consuming. Moreover, the manner of interaction between user and device can be difficult for some users or adversely impact the accuracy of the testing. As a result there remains a need for improvement in the field of visual acuity testing.
Visual acuity testing, such as the Amsler grid, is commonly used for the detection of metamorphopsia—distortion of the image due to retinal detachment or edema. During metamorphopsia, a set of horizontal and vertical straight lines, appears wavy and parts of the grid may be absent or dim. Metamorphopsia is mainly associated with wet phase of age-related macular degeneration (i.e. choroidal neovascularization), pathological myopia, histoplasmosis syndrome, choroidal rupture and multifocal choroiditis.
During the conventional Amsler grid test patients are asked to look at the fixation point in the center of the grid, and mark the areas on the grid that appear distorted, absent, or dim. Even though the distortion is readily visible to patients, marking its location on the grid is often a very challenging task. The problem is that in some cases as soon as a person begins to draw his sight instinctively moves from the fixation point to the pen or a finger on a touch screen. This shifts the distorted area away, and the patient does not see the area he is marking as distorted anymore. Fixating away from the drawing tool (so called off-center fixation) requires significant cognitive effort which is often beyond the capabilities of the average patient affected by age-related macular degeneration. Typically, patients can easily tell whether they see distortions on the grid, but it can be hard to quantify the extent of these distortions by marking the grid. In some cases patients can have dexterity issues that make marking the grid accurately difficult or impractical.
Patients can be discouraged from taking tests on their own if the tests are difficult, time consuming, or have too many steps. As a result, it is desirable to design a test that is easy for the patient to take on their own time and that requires relatively few steps to achieve a useful result.